The effect of chemical additives in microorganism fermentations has been extensively studied. For example, P. P. Williams et al, App. Microbiology, 11, 517 (1963) describe rumen bacteria and protozoal responses to insecticide substrate; J. J. O'Connor et al, J. Animal Sci., 33, 662 (1971) describe the in vivo effect of chemical additives on production of volatile fatty acids by rumen microorganisms; and L. W. Varner et al, J. Animal Sci., 33, 1110 (1971), describe the influence of ammonium salts upon rumen fermentation by steers; and T. W. Dowe et al, J. Animal Sci., 16, 93 (1957) describe the effect of corn treated with fungicides (N-trichloromethylthio-delta.sup.4 -tetrahydrophthalimide) on the performance of fattening steers.